The purpose of this project is to examine the input-output organization of neurons in the motor cortex. Rats have been chosen as the primary experimental animal since they are readily available and have small, lissencephalic brains. Neuroanatomical and neurophysiological techniques are being employed to characterize the primary motor cortex (MI) and other closely related cortical areas in rats and determine their connectional relationships with other neural structures. Immunocytochemical techniques are being used to identify the transmitters of cortical neurons. Neuronal activity will be monitored in the forelimb area of MI cortex in awake, behaving rats and the contribution of inputs to these neurons in generating or modulating discharge patterns during movements will be assessed. Intrinsic cortical circuits are being studied by intracellular injection of a tracer, horseradish peroxidase, to demonstrate the connectional relationship between intrinsic and projection neurons in the cortex.